Colds and Influenza (the Flu)

Description

Alternative Names

Complications

Colds rarely cause serious complications. In about 1% of cases, a cold can lead to other complications, such as sinus or ear infections. It can also aggravate asthma and, in uncommon situations, increase the risk for lower respiratory tract infections.

Ear Infections. The rhinovirus infection, a major cause of colds, also commonly predisposes children to ear infections, possibly by obstructing the Eustachian tube, which leads to the middle ear. Viruses may even attack the ear directly. In one study, 74% of patients with rhinovirus colds had pressure abnormalities in their middle ear.

Sinusitis. Between 0.5% and 5% of people with colds develop sinusitis, an infection in the sinus cavities (air-filled spaces in the skull). Sinusitis is usually mild, but if it becomes severe, antibiotics generally eliminate further problems. In rare cases, however, sinusitis can be serious.

Lower Respiratory Tract Infections. The common cold poses a risk for bronchitis and pneumonia in nursing home patients and other people who may be susceptible to infection. Some experts believe that the rhinovirus may play a more significant role than the flu in causing lower respiratory infections in such people.

Aggravation of Asthma. Rhinovirus infections can acerbate asthma in both children and adults and has reported to be the most common infectious organism associated with asthma attacks. Some studies have reported the common cold being associated with between 33% and 71% of severe asthma episodes. Research suggests that colds promote allergic inflammation and increase the intensity of airway responsiveness for weeks.

Complications of Influenza

In general, the flu is usually self-limited and not serious. Influenza is responsible, however, for 15% to 30% of the excess number of hospitalizations that occur in winter. About 1% of people who contract the flu end up in the hospital. An estimated 36,000 people currently die each year of influenza-related complications. The highest risks for serious complications occur in people over 65 years old and in those with other medical conditions. Influenza A is the most severe strain and causes an estimated average of 142,000 hospitalizations per year. Influenzas B and C tend to be milder.

Pneumonia. Pneumonia is the major serious complication of influenza and can be very serious. It can develop about five days after viral influenza. It is an uncommon event, however. It nearly always occurs in high-risk individuals, such as the following:

• The elderly. Older adults account for more than 90% of the deaths caused by influenza and pneumonia. The growing elderly population will most likely cause an increase in deaths from influenza. Nursing homes patients are especially hard-hit by flu epidemics, with fatality rates as high as 30%.
• People with weakened immune systems, such as AIDS patients.
• Very young children. Children under one year who develop flu have a very high risk for pneumonia. Experts estimate that about 25% of severe lung infections in children are due to influenza. It is often difficult to tell, however, whether pneumonia in small children is related to influenza or caused by respiratory syncytial virus (RSV), which is the major viral cause of infant pneumonia.
• Hospitalized patients and anyone with serious medication conditions, such as diabetes or heart, lung, or circulation disorders. Chronic lung disease poses a very high risk, particularly for children and the elderly. In a 2002 study, influenza and respiratory syncytial virus were responsible for 15% to 33% of hospitalizations in children with asthma and 9% of deaths in adults over 65 with chronic lung disease.
• Drug abusers who use needles.

Combinations of these factors increase the risk. It should be noted that pneumonia is an uncommon outcome of influenza in healthy adults.

Complications in the Central Nervous System in Children. Influenza increases the risk for complications in the central nervous system of small children. In a 2001 Chinese study, children hospitalized with influenza A had a higher risk for fever related seizures than children with other upper respiratory tract infections. In rare cases, influenza can lead to meningitis and encephalitis (inflammations in the central nervous system). The risks decline after age one, but are still elevated in children aged three to five.

Pandemics. Every year, influenza strikes millions of people worldwide. Influenza epidemics are most serious when they involve a new strain against which most people are not immune. Such so-called pandemics can infect more than one fourth of the world's population within a three-month period. For example, the Spanish flu in 1918 and 1919 killed 20 million people in the U.S. and Europe and 17 million in India. Although pandemics are still of great concern, there have been major improvements in private and public health since then, including the discovery of antibiotics to treat bacterial complications, new anti-viral agents and vaccines, and intensive world-wide surveillance of outbreaks.